Seeing the casting number on your mount, it's likely an original lower mount being it's just one number off from the actual book listed part number. It's kinda how Chevy did their parts identification with casting numbers, but since they mostly stopped listing the casting numbers in the mid '60s and later parts books in the item description, it makes it a little hair pulling to try and confirm what you have.
Anyhow, seeing the pics of what you have, I think your harmonic balancer and water pump and pulleys are good for use as is. On the realignment of the alternator, you have a couple of options IMHO.
First is to swap the mount with something that will move your existing alternator forward to attain alignment as suggested before with different bracket and spacers.
A second possibility is to purchase a slightly different style alternator (see screen shot below) from this sample
linked source. It would allow you to relocate the alternator forward using the existing lower mount, by placing the forward lower mount ear in front of the mount forward pivot ear. Then use a longer bolt with spacers/washers and nut to attach to the lower mount to align with the other pulleys.
In both these cases, you will also need to modify and/or add spacers to the upper mount adjusting swing arm too.
Just throwing stuff at the wall to see if something might help you out.
